Electroplating system having auxiliary electrode exterior to main reactor chamber for contact cleaning operations

ABSTRACT

A system for electroplating a semiconductor wafer is set forth. The system comprises a first electrode in electrical contact with the semiconductor wafer and a second electrode. The first electrode and the semiconductor wafer form a cathode during electroplating of the semiconductor wafer. The second electrode forms an anode during electroplating of the semiconductor wafer. A reaction container defining a reaction chamber is also employed. The reaction chamber comprises an electrically conductive plating solution. At least a portion of each of the first electrode, the second electrode, and the semiconductor wafer contact the plating solution during electroplating of the semiconductor wafer. An auxiliary electrode is disposed exterior to the reaction chamber and positioned for contact with plating solution exiting the reaction chamber during cleaning of the first electrode to thereby provide an electrically conductive path between the auxiliary electrode and the first electrode. A power supply system is connected to supply plating power to the first and second electrodes during electroplating of the semiconductor wafer and is further connected to render the first electrode an anode and the auxiliary electrode a cathode during cleaning of the first electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of International PCT PatentApplication No. PCT/US98/00126 designating the US, filed Jan. 6, 1998,entitled ELECTROPLATING SYSTEM HAVING AUXILIARY ELECTRODE EXTERIOR TOMAIN REACTOR CHAMBER FOR CONTACT CLEANING OPERATIONS, which is acontinuation in-part from U.S. patent application Ser. No. 08/940,670,filed Sep. 30, 1997, and U.S. patent application Ser. No. 08/940,930,filed Sep. 30, 1997, now U.S. Pat. No. 6,099,712.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

In the production of semiconductor integrated circuits and othersemiconductor articles from semiconductor wafers, it is often necessaryto provide multiple metal layers on the wafer to serve as interconnectmetallization which electrically connects the various devices on theintegrated circuit to one another. Traditionally, aluminum has been usedfor such interconnects, however, it is now recognized that coppermetallization may be preferable.

The application of copper onto semiconductor wafers has, in particular,proven to be a great technical challenge. At this time coppermetallization has not fully achieved commercial reality due to practicalproblems of forming copper layers on semiconductor devices in a reliableand cost efficient manner.

The industry has sought to plate copper onto a semiconductor wafer byusing a damascene electroplating process where holes, more commonlycalled vias, trenches and other recesses are used in which the patternof copper is desired. In the damascene process, the wafer is firstprovided with a metallic seed layer which is used to conduct electricalcurrent during a subsequent metal electroplating step. The seed layer isa very thin layer of metal which can be applied using one or more ofseveral processes. For example, the seed layer of metal can be laid downusing physical vapor deposition or chemical vapor deposition processesto produce a layer on the order of 1000 angstroms thick. The seed layercan advantageously be formed of copper, gold, nickel, palladium, andmost or all other metals. The seed layer is formed over a surface whichis convoluted by the presence of the vias, trenches, or other devicefeatures which are recessed.

In damascene processes, the copper layer that is electroplated onto theseed layer is in the form of a blanket layer. The blanket layer isplated to an extent which forms an overlying layer, with the goal ofcompletely providing a copper layer that fills the trenches and vias andextends a certain amount above these features. Such a blanket layer willtypically be formed in thicknesses on the order of 10,000-15,000angstroms (1-1.5 microns).

After the blanket layer has been electroplated onto the semiconductorwafer, excess metal material present outside of the vias, trenches orother recesses is removed. The metal is removed to provide a resultingpatterned metal layer in the semiconductor integrated circuit beingformed. The excess plated material can be removed, for example, usingchemical mechanical planarization. Chemical mechanical planarization isa processing step which uses the combined action of a chemical removalagent and an abrasive which grind and polish the exposed metal surfaceto remove undesired parts of the metal layer applied in theelectroplating step.

Automation of the copper electroplating process has been elusive, andthere is a need in the art for improved semiconductor plating systemswhich can produce copper layers upon semiconductor articles which areuniform and can be produced in an efficient and cost-effective manner.More particularly, there is a substantial need to provide a copperplating system that is effectively and reliably automated.

In the electroplating of semiconductor wafers, an anode electrode isdisposed in a plating bath and the wafer with the seed layer thereon isused as a cathode with the face of the wafer that is to be platedcontacting an upper surface of the plating bath. The semiconductor waferis held by a support system that also provides be requisite cathodepotential to the wafer. The support system may comprise conductivefingers that secure the wafer in place and also contact the wafer inorder to conduct electrical current for the plating operation.

During the electroplating process, the conductive fingers as well as besemiconductor wafer are plated with the plating metal, such as copper.One potential problem that occurs in such a process is the build up ofplating metal deposits on the conductive finger. These deposits may: 1)result in unintended attachment of the conductive finger while incontact with the wafer such that upon disengagement of the conductivefinger with the wafer surface, some of the plated surface may tear awayand fall off as particles; 2) introduce variability in the current beingconducted through the contact and ultimately across the plated surface;and 3) result in small particles breaking off of the deposits on theconductive finger or off of the wafer which may enter the plating bath,and ultimately lodge directly on the wafer surface during plating orcontaminate subsequently plated wafers. These effects may eachindependently or in combination create irregularities in the platedsurface or result in other defects in the wafer. Additionally, theseeffects may also contribute to reduced wafer to wafer uniformity.

One manner in which the plating may be removed from the electrodefingers is to manually remove the conductive electrode fingers forcleaning when a specified level of plating or deposits has built-up onthe finger contact surface. This is undesirable, however, because itcauses significant down time in the electroplating processing,particularly in continuous wafer plating operations. Significant loss ofwafer throughput and higher processing costs are associated with thiscourse of action. It would be more desirable to develop a method forcleaning the deposits off of the electrode and segregating the resultingparticles from the plating process while at the same time minimizing thedowntime of the production process.

BRIEF SUMMARY OF THE INVENTION

A system for electroplating a semiconductor wafer is set forth. Thesystem comprises a first electrode in electrical contact with thesemiconductor wafer and a second electrode. The first electrode and thesemiconductor wafer form a cathode during electroplating of thesemiconductor wafer. The second electrode forms an anode duringelectroplating of the semiconductor wafer. A reaction container defininga reaction chamber is also employed. The reaction chamber comprises anelectrically conductive plating solution. At least a portion of each ofthe first electrode, the second electrode, and the semiconductor wafercontact the plating solution during electroplating of the semiconductorwafer. An auxiliary electrode is disposed exterior to the reactionchamber and positioned for contact with plating solution exiting thereaction chamber during cleaning of the first electrode to therebyprovide an electrically conductive path between the auxiliary electrodeand the first electrode. A power supply system is connected to supplyplating power to the first and second electrodes during electroplatingof the semiconductor wafer and is further connected to render the firstelectrode an anode and the auxiliary electrode a cathode during cleaningof the first electrode.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an electroplating system that mayuse an auxiliary electrode in accordance with the present invention.

FIG. 2 is a schematic block diagram of one embodiment of the inventioncomprising an auxiliary electrode in a fluid outlet tube.

FIG. 3 is a schematic block diagram of one embodiment of the inventioncomprising an auxiliary electrode in a reservoir container exterior tothe reaction chamber.

FIG. 4 is a schematic block diagram of one embodiment of the inventioncomprising an auxiliary electrode disposed about an upper exterior rimof the reaction cup.

FIGS. 5A, 5B and 5C illustrate a process bowl assembly that may be usedto implement the embodiment of the invention illustrated in FIG. 4.

FIG. 6 illustrates a further embodiment of a process bowl assembly thatmay be used to implement the embodiment of the invention illustrated inFIG. 4.

FIG. 7 illustrates one embodiment of a reactor assembly that may be usedto implement the disclosed electroplating system.

FIG. 8 illustrates a further embodiment of a reactor assembly that maybe used to implement the disclosed electroplating system.

FIG. 9 illustrates one embodiment of a wafer support/spin assembly thatmay be used to implement electroplating system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of a plating system, shown generallyat 50, for electroplating a metallization layer, such as a patternedcopper metallization layer, on, for example, a semiconductor wafer 55.The illustrated system generally comprises a vision system 60 thatcommunicates with a main electroplating control system 65. The visionsystem 60 is used to identify the particular product being formed on thesemiconductor wafer 55 before it is placed into an electroplatingapparatus 70. With the information provided by the vision system 60, themain electroplating control system 65 may set the various parametersthat are to be used in the electroplating apparatus 70 to electroplatethe metallization layer on the wafer 55.

In the illustrated system, the electroplating apparatus 70 is generallycomprised of an electroplating chamber 75, a rotor assembly 80, and astator assembly 85. The rotor assembly 80 supports the semiconductorwafer 55, a current control system 90, and a current thief assembly 95.The rotor assembly 80, current control system 90, and current thiefassembly 95 are disposed for co-rotation with respect to the statorassembly 85. The chamber 75 houses an anode assembly 100 and containsthe solution 105 used to electroplate the semiconductor wafer 55.

The stator assembly 85 supports the rotor assembly 80 and it'sassociated components. A stator control system 110 may be disposed infixed relationship with the stator assembly 85. The stator controlsystem 110 may be in communication with the main electroplating controlsystem 65 and may receive information relating to the identification ofthe particular type of semiconductor device that is being fabricated onthe semiconductor wafer 55. The stator control system 110 furtherincludes an electromagnetic radiation communications link 115 that ispreferably used to communicate information to a correspondingelectromagnetic radiation communications link 125 of the current controlsystem 90 used by the current control system 90 to control current flow(and thus current density) at individual portions of the current thiefassembly 95. A specific construction of the current thief assembly 95,the rotor assembly 80, the stator control system 110, and the currentcontrol system 90 is set forth in further detail below.

In operation, contacts 120 make electrical contact with thesemiconductor wafer 55. The semiconductor wafer 55 is then lowered intothe solution 105 in minute steps by, for example, a stepper motor or thelike until the lower surface of the semiconductor wafer 55 makes initialcontact with the solution 105. Such initial contact may be sensed by,for example, detecting a current flow through the solution 105 asmeasured through the semiconductor wafer 55. Such detection may beimplemented by the stator control system 110, the main electroplatingcontrol system 65, or the current control system 90. Preferably,however, the detection is implemented with the stator control system110.

Once initial contact is made between the surface of the solution 105 andthe lower surface of the semiconductor wafer 55, the wafer 55 ispreferably raised from the solution 105 by a small distance. The surfacetension of the solution 105 creates a meniscus that contacts the lowersurface of the semiconductor wafer 55 that is to be plated. By using theproperties of the meniscus, plating of the side portions of the wafer 55is inhibited.

Once the desired meniscus has been formed at the plating surface,electroplating of the wafer may begin. Specific details of the actualelectroplating operation are not particularly pertinent to the use ordesign of present invention and are accordingly omitted.

FIG. 2 illustrates one embodiment of a semiconductor waferelectroplating system that facilitates in-situ cleaning of the contacts120. As illustrated, the system, shown generally at 200, includes areactor cup 205 that defines the processing chamber 75. The anode 100 isdisposed at the bottom of the reactor cup 205 while the semiconductorwafer 55 functioning as the cathode is disposed at the upper portion ofthe reactor cup 205. As noted above, the wafer 55 is supported so thatonly the bottom face thereof is in contact with the plating solution.Optionally, a diffuser assembly 210 is disposed between the anode 100and the semiconductor wafer 55.

Plating solution is supplied to the processing chamber 75 through afluid inlet 215 that opens to the bottom of lever processing cup 205 theplating fluid fills chamber 75 and provides a conductive path betweenthe anode 100 and the semiconductor wafer 55 to thereby form a completeelectroplating circuit. A continuous flow of the plating fluid into thechamber 75 is preferable. As such, processing solution must the removedfrom the processing chamber 75 at the same rate that it is suppliedthrough the inlet 215. To this end, the processing cup 205 is disposedwithin a reservoir bowl 220. Plating solution fills chamber 75 throughinlet 215 and overflows from the reactor cup 205. The overflowing fluidflows over the upper rim of cup 205 and into the interstitial regionbetween the outer perimeter of cup 205 and he inner perimeter ofreservoir bowl 220. Processing solution is allowed to exit from thereservoir bowl 220 through a fluid outlet assembly 225. The fluid outletassembly 225 is preferably comprised of an outlet to 230, an externalelectrode 235, and a control valve 240 disposed in the fluid pathbetween the reservoir bowl 220 and the external electrode 235.

During normal wafer plating operations, switch for 245 is closed whileswitch 250 is open. This allows the supply 255 to provide the requisiteplating power to execute a plating operation of the semiconductor wafer55.

After the electroplating process is completed, the semiconductor wafer55 is removed and in-situ cleaning of the contact electrodes 120 may beconducted. To this end, switch 245 is opened while switch 250 is closedto thereby connect supply 280 to the contact electrodes 120 and theexternal electrode 235. This effectively makes the electrode contacts120 function as anodes and the external electrode 235 function as thecathode. Processing fluid flow from reservoir bowl 220 is controlled bycontrol valve 240 to maintain a level of the processing fluid in thereservoir bowl 220 at a level which maintains electrical contact throughthe plating solution between the electrodes 120 and external electrode235. The resulting reverse current may be provided at a voltagepotential in the approximate range of 0.1-100 volts, alternatively inthe approximate range of 0.1-20 volts, or alternatively in theapproximate range of 1-10 volts between the auxilliary electrode and thewafer contact electrodes. The voltage potential may vary dependent onthe number of semiconductor workpieces that are processed through anormal operating cycle, etc.

It should be noted that the two supply configuration illustrated here ismerely for illustrative purposes. A single supply capable of providingboth the plating and cleaning power may be used with any suitableswitching configuration.

With supply 280 connected, metal, such as copper, that was plated to theelectrodes 120 during electroplating above the wafer 55 may be partiallyor completely removed. Since this plating operation takes place in anelectrical circuit exterior to the processing chamber 75, anyby-products resulting from the cleaning operation fall exterior to thechamber 75 thereby maintaining the chamber in a relatively hygienicstate.

The foregoing cleaning operations may take place at various times. Forexample, the cleaning operation may occur after electroplating a singlesemiconductor wafer, five semiconductor wafers, ten semiconductorwafers, etc, during the manufacturing process. If a small number ofwafers is chosen, such cleaning may occur without disruptingmanufacturing operations. Generally, however, when more than 50semiconductor wafers have been processed, the duration of the cleaningoperation may become excessive thereby prohibiting such cleaningoperations from taking place during typical semiconductor wafermanufacturing operations. It will be recognized that the amount ofcopper plated on each wafer between cleaning cycles will effectivelydetermined how much copper is plated onto the contact electrodes 120 andthereby determine the duration of the in-situ cleaning operation.

Removed deposits may flow out the plating bath via the outlet tube 230and be collected in a particulate filter or disposed in an appropriatewaste removal and handling operation. If passed through a particulatefilter, the filtered solution may be reintroduced into the plating bath.This is desirable from both economic and waste handling perspectives.

If a particulate filter is used, it may comprise any material that iscapable of filtering or trapping particles, particularly thosecomprising deposits removed from the cleaned electrode contacts. Theparticulate filter ideally also allows passage of ions along with theplating bath solution passing through it. In this case, the filteredplating bath solution may be reintroduced into the plating bath with theassociated benefits described above. Materials suitable for use in theparticulate filter include those such as fritted glass.

An alternative placement of an external electrode for in-situ cleaningis illustrated in FIG. 3. In this embodiment, the external electrode 270is disposed at the bottom bottom of reservoir bowl 220 and is in theform all of an annular electrode disposed about the inlet tube 215.

A still further alternative placement of the external electrode isillustrated in FIG. 4. In the illustrated embodiment, the externalelectrode 281 is disposed about the outer upper periphery of theprocessing cup 205. Placement of the external electrode 281 at the outerupper periphery of the processing cup 205 increases the likelihood of aproper electrical connection through the fluid during cleaningoperations. Additionally, since the external electrode 281 is disposedin a region having high velocity processing fluid flow, any residueparticulates that may inhibit electrode cleaning operations may be wipedfrom the electrode 281 by the processing fluid.

In each of the embodiments illustrated in FIGS. 3 and 4, operation ofthe apparatus during electroplating and cleaning operations aresubstantially similar to those set forth in connection with theembodiment of FIG. 2.

The foregoing apparatus and associated methods are suitable forincreasing the number of wafers produced in a specific time interval inan electroplating process as compared to systems without such a cleaningoperation. Because the cleaning cycles can be invoked quickly andeasily, in some instances within standard electroplating processoperating sequences, the electrode contacts remain cleaner for longerperiods of time as compared to electrodes without such cleaning. Thisallows for more wafers to be processed within the same qualityparameters over the same period of time. Systems using such methods alsoincrease wafer processing throughput by avoiding lengthy downtimeassociated with shutting down electroplating systems to manuallyreplace/clean the conductive finger electrodes.

The apparatus and associated methods also enhance the uniformity of thesurface plating compared to systems without such a cleaning operation.An electroplated surface, particularly on a semiconductor wafer, isideally void of irregularities. The desired uniformity is, in part, afunction of the current density across the wafer surface duringelectroplating. Clean contact between the conductive electrode contactsurface and the wafer surface is critical to achieving uniformity. Thecleaner electrode contacts consequently improve uniform current densityon the wafer surface during electroplating, giving rise to improvedsurface uniformity across the wafer surface and provide greater wafer towafer uniformity (that is, the quality of a wafer as compared to asubsequently plated wafer in the same process) compared to methodswithout such cleaning operations.

The use and placement of the auxiliary electrodes allows for theparticles and contaminates in the plating bath solution to be segregatedand removed from the reaction system, thus preventing the particles andcontaminates from lodging onto subsequently processed wafers and therebycreating irregularities on those surfaces. The auxiliary electrode andfiltering configuration also provides a convenient means for cleaningthe finger electrode and plating solution with minimal intrusion intothe reactor system as compared with manual replacement of the fingerelectrode.

FIGS. 5A, 5B, and 5C illustrate a more particular embodiment of theapparatus shown in general form in FIG. 4. As illustrated, the apparatusincludes an auxiliary electrode support 300 that supports electrode ring305. The electrode ring 305 is positioned between a rim 310 and diffuser210, which is positioned above anode assembly 100. The combinedassemblies are positioned within processing cup weldment 205 which, inturn, is disposed in reservoir bowl weldment 220. The auxiliaryelectrode ring 305 is secured to support 300 such that the electrodering 305 is below the plating solution meniscus and outside of theplating bath. In such position it is capable of contacting with overflowsolution flowing from the bath.

In a further embodiment, the system described directly above mayoptionally comprise a particulate filter. The particulate filter may bepositioned at any appropriate place that allows for the plating bathsolution containing particulate matter to pass through it, such as inthe space between the plating bath wall and the outer chamber wall or inan exit tube attached to that space. In such a configuration, theparticulate filter comprises any material that is capable of filteringor trapping particles, particularly those comprising deposits removedfrom the cleaned electrode contacts. The particulate filter ideally alsoallows passage of ions along with the plating bath solution passingthrough it. In this case, the filtered plating bath solution may bereintroduced into the plating bath with the associated benefitsdescribed above. Materials suitable for use in the particulate filterinclude those such as fritted glass.

Various other reactor apparatus configurations are also suitable for usewith one or more of the external electrode configurations discussedabove. One such reactor is shown in FIGS. 6 and 7.

In the reactor embodiment illustrated in FIGS. 6 and 7, a process bowlor plating chamber 616 having a bowl side 617 and a bowl bottom 619. Theprocess bowl is preferably circular in a horizontal cross section andgenerally cylindrical in shape although the process bowl may be taperedas well.

A cup assembly 620 is disposed within process bowl 616. Cup assembly 620includes a fluid cup 621 having a cup side 622 and a cup bottom 623. Aswith the process bowl, the fluid cup 621 is preferably circular inhorizontal cross section and cylindrical in shape, although a taperedcup may be used with a tapered process bowl.

Process fluid is provided to the process bowl 616 through fluid inletline 625. Fluid inlet line rises through bowl bottom opening 627 andthrough cup fluid inlet opening 624 and terminates at inlet line endpoint 631. Fluid outlet openings 628 are disposed within the fluid inletline 625 in the region between the cup fluid inlet opening 624 and fluidline end point 631. In this way, fluid may flow from the fluid inletline 625 into the cup 621 by way of the inlet plenum 629.

The cup assembly 620 preferably includes a cup filter 630 which isdisposed above the fluid inlet openings and securely fits between theinner cup wall 622 and the fluid inlet line 625 so that fluid must passthrough the filter before entering the upper portion of cup 621.

The cup assembly 620 is provided with a metallic anode 634. Anode 634 issecured within the cup assembly by attaching it to the end point 631 ofthe fluid inlet line. Anode 634 is thus disposed above the cup filter630 as well as above fluid inlet opening 628. Anode 634 is preferablycircular in shape and of a smaller diameter than the inside diameter ofcup 621. Anode 634 is secured to the end point 631 of fluid inlet line625 so as to center the anode 634 within cup 621 creating an annular gapor space 635 between the inner cup wall 622 and the edge of anode 634.Anode 634 should be so placed such as to cause the anode annular opening635 to be of a constant width throughout its circumference.

The outer cup wall 636 has a smaller diameter than the inside diameterof bowl 616. Cup assembly 620 is positioned within bowl 616 such that afirst annular space or process fluid overflow space 632 is formedbetween bowl side 617 and cup outer wall 636. The cup assembly is morepreferably positioned such that the annular fluid overflow space 632 isof a constant width throughout its circumference. Cup assembly 620 isfurther positioned within bowl 616 such that cup upper edge 633 is belowbowl upper edge 637. Cup 621 is preferably height-adjustable withrespect to bowl upper edge 637, as more fully described below.

Bowl bottom 619 is configured so as to have a large open area allowingthe free transfer of fluid therethrough. In the preferred embodiment,this is achieved by the structure shown in FIG. 6, wherein the processbowl bottom 619 is composed of crossbars 626 which intersect at bowlbottom center plate 639 creating fluid return openings 638. Bowl bottomcenter plate 639 is provided with bowl bottom opening 627 to allow fluidinlet line 625 to pass therethrough. In the illustrated embodiment, thebowl sides 617 below the reservoir top 618 are also similarlyconstructed so that bowl sides below reservoir top 618 are composed of 4rectangular sections which then turn inward towards bowl bottom centerplate 639 intersecting thereat. Such a configuration allows for a highdegree of fluid flow to pass through the bowl lower portion which isdisposed within reservoir 604. Thus, in operation, process fluid isprovided through process fluid inlet line 625 and discharges throughfluid outlet openings 628 within the lower part of the cup assembly 620.By virtue of cup filter 620, fluid entering the fluid inlet plenum 629is distributed across the plenum and then flows upward through filter630 to the bottom of anode 634.

From the top side of filter 630, the process fluid continues to flow inan upward direction by virtue of a continuous supply of process fluidthrough process inlet line 625. The process fluid flows around theannular gap 635 between the anode 634 and the inner cup wall 622. As theprocess fluid continues to well up within cup 621, it will eventuallyreach upper cup edge 633 and will overflow into the overflow annular gap632 between the outer cup wall 636 and the inner wall of bowl 616.

The overflowing fluid will flow from the overflow gap 632 downwardthrough the gap and back into reservoir 604 where it will be collectedfor reuse, recycling, or disposal. In this manner, no process fluidreturn line is required and no elaborate fluid collection system isnecessary to collect surplus fluid from the process.

As a further advantage, the location of the cup filter 630 and anode 634within the cup 621 provides an even distribution of fluid inlet into thecup. The even distribution beneficially assists in providing a quiescentfluid surface at the top of cup 621. In like manner, maintaining aconstant distance between the outer wall of cup 636 and the inner wallof bowl 616 in providing the overflow gap 632 will assist in providingan even flow of fluid out of cup 621 and into the reservoir 604. Thisfurther beneficially assists in providing the desired quiescence stateof the process fluid at the top of cup 621.

The material selection for cup filter 620 will be dictated by theprocess and other operating needs. Typically, the filter will have thecapability of filtering particles as small as 0.1 microns. Likewise, thechoice of materials for anode 634 will be dictated by the desired metalto be electroplated onto the workpiece. For example, an anode comprisedprimarily of copper may be used for electroplating copper onto asemiconductor wafer.

While the reactor has been described particularly for an electroplatingprocess, it can be seen that for a process where a flow of fluid isrequired but no anode is required removing the anode 634 from the cupassembly 603 will provide a quiescent pool of liquid for the process. Insuch an arrangement, the end point 631 of the fluid inlet line 625 wouldbe capped or plugged by a cap or plug rather than by the anode 634.

To assist in ensuring that process fluid overflows into the annular gap632 evenly, the cup upper edge 633 is levelled such that fluid does notflow off of one side of cup 621 faster than on another side. Toaccomplish this objective, levelers are preferably provided with theprocess bowl assembly 603.

Turning now to FIG. 7, a representational process bowl assembly is shownin cross section along with a representational workpiece support 401 toillustrate an entire electroplating assembly comprising an auxiliaryelectrode 1015 (shown in FIG. 6.) Plating chamber assembly 603 ispreferably provided with levelers 640 (only one of which is shown inthis view) which allow the plating chamber assembly to be leveledrelative to the top of reservoir 618. The levelers may comprise jackscrews threaded within the edge of module deck plate 666 and in contactwith the process module frame 606 so as to elevate the process bowlassembly 603 relative to the process module 20. The process bowlassembly 603 is preferably provided with three such bowl levelersdistributed about the bowl periphery. This allows for leveling in bothan X and Y axis or what may be generically described as “left and rightleveling and front and rear leveling.”

Since process bowl assembly 603 is free to move with respect to fluidreservoir 604, when process bowl assembly 603 is fit closely withinfluid reservoir 604 as shown in FIG. 6, the process bowl/fluid reservoirjunction preferably has a compliant bowl seal 665 disposed therebetweento allow movement of the process bowl 616 with respect to reservoirinner wall 609. Compliant seal 665 further prevents process fluid frompassing through the opening between the process bowl and the reservoirwall.

Cup assembly 620 is preferably provided with cup height adjuster 641.The cup height adjuster shown and described herein is comprised of a cupheight adjustment jack 643 which is positioned about an external portionof inlet line 625. Cup 621 is secured to cup height adjustment jack 643with cup lock nut 642. Cup lock nut 642 is used to secure cup 621 in itsheight position following adjustment. The upper end of cup heightadjustment jack 641 is provided with adjustment tool access holes 667 toallow for adjusting of the height of the cup from the top of the bowlrather than the underside. The cup height adjuster 641 may additionallybe provided with a fluid seal such as an o-ring (not shown) disposedwithin the annular space formed between the adjustment jack 643 and thecup bottom 623.

The process bowl assembly 602 is more preferably provided with anadditional height adjuster for the anode 634. Anode height adjuster 648is formed by mounting the anode 634 on the threaded anode post 664. Athreaded anode adjustment sleeve 663 is used to connect the threadedupper end of inlet line 625. Anode adjustment sleeve 663 is providedwith sleeve openings 668 to allow fluid to pass from fluid outletopenings 628 into the inlet plenum 629. The space between the bottom ofanode post 664 and the upper end of fluid inlet line 625, and bounded bythe anode adjustment sleeve 663, defines a fluid outlet chamber 662.Fluid outlet chamber is of variable volume as the anode post 664 movesupward and downward with height adjustment of the anode 634.

On the bowl leveler 640 and the height adjusters 641 and 646 describedabove, it is additionally desirable to provide them with lockingmechanisms so that once the desired positioning of the device (i.e., thebowl, the cup, or the anode) is achieved, the position may be maintainedby securing the adjusters so that they do not move out of adjustment asa result of vibration or other physical events.

Allowing independent height adjustment of the cup and anode each withrespect to the bowl provides a large degree of flexibility in adjustingthe process bowl assembly 603 to accommodate a wide selection ofprocesses.

A further electroplating processing station that may use one or moreexternal electrodes for in-situ cleaning of the wafer electrode contactsis illustrated in FIG. 8. The two principal parts of processing station900 are the wafer rotor assembly, shown generally at 906, and theelectroplating bowl assembly 303.

FIG. 8 shows the electroplating bowl assembly 303. The bowl assemblycomprises a process bowl or plating vessel 316 having an outer bowl sidewall 317, bowl bottom 319, and bowl rim assembly 917. The process bowlis preferaoly circular in horizontal cross-section and generallycylindrical in shape although other shapes may be possible.

The bowl assembly 303 includes a cup assembly 320 which is disposedwithin a process bowl vessel 317. Cup assembly 320 includes a fluid cupportion 321 holding the chemistry for the electroplating process. Thecup assembly also has a depending skirt 371 which extends below the cupbottom 323 and may have flutes open therethrough for fluid communicationand release of any gas that might collect as the chamber below fillswith liquid. The cup is preferably made from polypropylene or othersuitable material.

A lower opening in the bottom wall of the cup assembly 320 is connectedto a polypropylene riser tube 330 which is adjustable in height relativethereto by a threaded connection. A first end of the riser tube 330 issecured to the rear portion of an anode shield 393 which supports anode334. A fluid inlet line 325 is disposed within the riser tube 330. Boththe riser tube 330 and the fluid inlet line are secured with theprocessing bowl assembly 303 by a fitting 362. The fitting 362 canaccommodate height adjustment of both the riser tube and line 325. Assuch, the connection between the fitting 362 and the riser tube 330facilitates vertical adjustment of the anode position. The inlet line325 is preferably made from a conductive material, such as titanium, andis used to conduct electrical current to the anode 324, as well assupply fluid to the cup.

Process fluid is provided to the cup through fluid inlet line 325 andproceeds therefrom through fluid inlet openings 324. Plating fluid thenfills the chamber 904 through opening 324 as supplied by a plating fluidpump (not shown) or other suitable supply.

The upper edge of the cup side wall 322 forms a weir which limits thelevel of electroplating solution within the cup. This level is chosen sothat only the bottom surface of wafer W is contacted by theelectroplating solution. Excess solution pours over this top edgesurface into an overflow chamber 345. The level of fluid in the chamber345 is preferably maintained within a desired range for stability ofoperation by monitoring the fluid level with appropriate sensors andactuators. This can be done using several different outflowconfigurations. A preferred configuration is to sense a high levelcondition using an appropriate sensor and then drain fluid through adrain line as controlled by a control valve. It is also possible to usea standpipe arrangement (not illustrated), and such is used as a finaloverflow protection device in the preferred plating station. Morecomplex level controls are also possible.

The outflow liquid from chamber 345 is preferably returned to a suitablereservoir. The liquid can then be treated with additional platingchemicals or other constituents of the plating or other process liquidand used again.

In preferred use of the apparatus for electroplating, the anode 334 is aconsumable anode used in connection with the plating of copper or othermetals onto semiconductor materials. The specific anode will varydepending upon the metal being plated and other specifics of the platingliquid being used. A number of different consumable anodes which arecommercially available may be used as anode 334.

FIG. 8 also shows a diffusion plate 375 provided above the anode 334 forproviding a more even distribution of the fluid plating bath across thewafer W. Fluid passages are provided over all or a portion of thediffusion plate 375 to allow fluid communication therethrough. Theheight of the diffusion plate is adjustable using diffuser heightadjustment mechanisms 386.

The anode shield 393 is secured to the underside of the consumable anode334 using anode shield fasteners 394 to prevent direct impingement bythe plating solution as the solution passes into the processing chamber904. The anode shield 393 and anode shield fasteners 394 are preferablymade from a dielectric material, such as polyvinylidene fluoride orpolypropylene. The anode shield is advantageously about 2-5 millimetersthick, more preferably about 3 millimeters thick.

The anode shield serves to electrically isolate and physically protectthe back side of the anode. It also reduces the consumption of organicplating liquid additives. Although the exact mechanism may not be knownat this time, the anode shield is believed to prevent disruption ofcertain materials which develop over time on the back side of the anode.If the anode is left unshielded, the organic chemical plating additivesare consumed at a significantly greater rate. With the shield in place,these additives are not consumed as quickly.

The wafer rotor assembly 906 holds a wafer W for rotation within theprocessing chamber 904. The wafer rotor assembly 906 includes a rotorassembly 984 having a plurality of wafer-engaging fingers 979 that holdthe wafer against features of the rotor. Fingers 979 are preferablyadapted to conduct current between the wafer and a plating electricalpower supply and may be constructed in accordance with variousconfigurations to act as current thieves.

The various components used to spin the rotor assembly 984 are disposedin a fixed housing 970. The fixed housing is connected to a horizontallyextending arm 909 that, in turn, is connected to a vertically extendingarm. Together, the arms 908 and 909 allow the assembly 906 to be liftedand rotated from engagement with the bowl assembly to thereby presentthe wafer to the wafer conveying assembly 60 for transfer to asubsequent processing station.

The workpiece support processing head holds a wafer W for rotationwithin the processing chamber 904. A rotor assembly 984 has a pluralityof workpiece-engaging fingers 979 that hold the wafer against featuresof the rotor. Fingers 979 are also preferably adapted to conduct currentbetween the wafer and a plating electrical power supply (not shown).

FIG. 8 also shows auxiliary electrode 1015 disposed annularly around thecup sidewall 322. In a cleaning operation, the plating solution flows(as indicated by “FLOW”) over the weir formed by cup sidewall 322 andover auxiliary electrode 1015 into the area between walls 317 and 322.

The workpiece support assembly 901 includes a processing head 906 whichis supported by an head operator 907. Head operator 907 includes anupper portion 908 which is adjustable in elevation to allow heightadjustment of the processing head. Head operator 907 also has a headconnection shaft 909 which is operable to pivot about a horizontal pivotaxis 910. Pivotal action of the processing head using operator 907allows the processing head to be placed in an open or face-up position(not shown) for loading and unloading wafer W. FIG. 7 shows theprocessing head pivoted into a face-down position in preparation forprocessing.

A variety of suitable head operators which provide both elevational andhorizontal pivoting action are possible for use in this system. Thepreferred operators are also fitted with positional encoders (not shown)which indicate both the elevation of the processing head and its angularposition as pivoted about horizontal head pivot axis 910.

FIGS. 8 and 9 show additional details of the preferred construction ofprocessing head 906. The processing head includes a main part whichmoves with and is relatively stationary with respect to the pivot shaft909. The main part supports a rotating assembly which will be describedin greater detail below.

The main part includes a processing head housing 970 and processing headframe 982. The processing head frame 982 includes a door plate 983. Adoor ring member 984 is joined to plate 983 using suitable fasteners toprovide a door assembly which serve as the principal parts covering theupper opening of the processing bowl when the processing head is matedwith the bowl.

The processing head frame also includes a frame-pivot shaft connection985 which includes two mounting rings which receive and securely connectwith the processing head pivot shaft 909. FIG. 9 shows that the pivotshaft connection mounting rings are made in two parts and secured byfasteners (not shown). The pivot shaft connection base 935 is secured tothe door plate 983 using fasteners.

Processing head 906 is generally round in shape when viewed in planview. The processing head main part includes a housing 970 which has afirst housing part 971 and a second housing part or housing cap 972. Theprocessing head housing 970 encloses a main part enclosure whichsurrounds a processing head main part mechanism chamber 973. Chamber 973is used to house additional processing head components, such as the spinmotor, the finger actuators, and related service lines, such asdiscussed more fully below.

The upper surface of the door ring member 984 is provided with a groovewhich receives the lower edge of the first housing piece 971. The outerperiphery of the door ring member also advantageously includes aperipheral groove 986 which mounts an inflatable door seal 987. Seal 987seals with portions of the processing bowl to form a more fluid-tightprocessing chamber therewithin.

The lower surface of the door ring member 984 is preferably providedwith an annular rotor receiving groove 988 which receives top peripheralportions of the rotor therein in close proximity. This constructionallows a gas purge (not shown) to be applied between the door and rotorto help prevent processing vapors from migrating behind the rotor andinto to the various mechanisms present in the main part of theprocessing head. The periphery of the door ring member is furtherprovided with a chamfered lower edge to facilitate mating with theprocessing bowl.

The processing head also includes a moving assembly in the form of aworkpiece holder 978. The workpiece holder includes fingers 979 forholding a semiconductor workpiece. In the illustrated embodiment, anactuator 961 is used to drive a drive plate 683 against an upper plate658 of finger actuators 960. When actuated in this manner, fingeractuators 960 cause fingers 979 to rotate and disengage from the wafer.Disengagement between plate 683 and plate 658 causes the actuators 960to drive and rotate fingers 979 into engagement with the wafer. Theelectrodes may comprise any suitable metal or combination of metals forelectrode purposes, i.e. they must be compatible with the reactionconditions and conductive. Such metals include copper, platinum,titanium or platinized metals.

The processing head main part also includes a workpiece holder drivewhich moves the workpiece holder relative to the main part of theprocessing head. The preferred action is for the workpiece holder driveto be in the form of a rotor drive which rotates the workpiece holder.The rotor drive can be an electric motor, pneumatic motor or othersuitable drive. As shown, the processing head includes an electricworkpiece spin motor 980.

The drive motor 980 has stator armatures 916 which drive motor shaft 918in rotational movement. Drive motor 980 is supported by bottom motorbearing 921 in bottom motor housing 922. Bottom motor housing 922 issecured to the main part of the processing head at a central opening inthe door plate 983. Motor 980 is also held in place by a top motorhousing 923. Drive motor 980 is rotationally isolated from top motorhousing 923 by a top motor bearing 927, which is disposed between thespin motor shaft 918 and the top motor housing. Both motor housings aresecured to the processing head frame 982 using fasteners 924 whichextend down through the motor housings and into the door plate 983. Thefasteners 924 also extend upwardly through frame extensions 925. Frameextensions 925 support a top frame piece 926. Cap 972 is screwed ontopiece 926 at mating threads along the lower interior portion of the cap.

The drive motor is preferably an electric motor provided with a supplyof electricity via wiring run through pivot shaft 909 or otherwiseextending to the processing head.

The wafer support head 906 may be used to rotate the wafer contactelectrodes during in-situ cleaning thereof. In such instances, theelectrode may rotate at an angular velocity in the approximate rangefrom about 1 revolution per minute to about 300 revolutions per minute,or alternatively from about 10 revolutions per minute to about 100revolutions per minute. The direction of the rotation may be changed atleast once during a cleaning cycle, or alternatively in the approximaterange from about every 10 seconds to about every 1 minute.

To provide process fluid to the process bowl assembly in theelectroplating module, the module is advantageously provided with fluidtransfer equipment. The fluid transfer equipment is provided to drawprocess fluid from a reservoir, supply it to the process bowl assembly,and return it to a common collection point. The equipment may include animmersible pump which is mounted in a reservoir. The reaction chambermay be provided with such a pump, which further comprises a fluidsuction or pump suction hitch that draws process fluid from thereservoir. The immersible pump pumps fluid by pump suction into the pumpbody and out through the fluid discharge or pump discharge. Theimmersible pump is preferably driven by an electric pump motor.

In alternate embodiments of the present system, a submersible pump maybe employed. An immersible pump has an advantage in that it may beeasily removed for servicing and the like. In yet another embodiment,individual pumps for each of the process bowl assemblies may be deployedor, process bowls assemblies may share a set of common pumps. Each suchpump would have a process fluid inlet suction and a process fluiddischarge.

Numerous modifications may be made to the foregoing system withoutdeparting from the basic teachings thereof. Although the presentinvention has been described in substantial detail with reference to oneor more specific embodiments, those of skill in the art will recognizethat changes may be made thereto without departing from the scope andspirit of the invention as set forth in the appended claims.

What is claimed is:
 1. A system for electroplating a semiconductor wafercomprising: a first electrode in electrical contact with thesemiconductor wafer, the first electrode and the semiconductor waferforming a cathode during electroplating of the semiconductor wafer; asecond electrode forming an anode during electroplating of thesemiconductor wafer; a reaction container defining a reaction chamber,the reaction chamber comprising an electrically conductive platingsolution, at least a portion of each of the first electrode, the secondelectrode, and the semiconductor wafer contacting the plating solutionduring electroplating of the semiconductor wafer; an auxiliary electrodedisposed exterior to the reaction chamber and positioned for contactwith plating solution exiting the reaction chamber during cleaning ofthe first electrode to thereby provide an electrically conductive pathbetween the auxiliary electrode and the first electrode; a power supplysystem connected to supply plating power to the first and secondelectrodes during electroplating of the semiconductor wafer, the powersupply system further connected to render the first electrode an anodeand the auxiliary electrode a cathode during cleaning of the firstelectrode.
 2. A system as claimed in claim 1, wherein the secondelectrode is disposed substantially entirely in the plating solution ofthe reaction chamber and the first electrode comprises at least oneconductive finger which supports a semiconductor wafer as thesemiconductor wafer, the at least one conductive finger being positionedto support the semiconductor wafer so that only one side of thesemiconductor wafer contacts the surface of the plating solution in thereaction chamber during electroplating thereof.
 3. A system as claimedin claim 1, wherein the auxiliary electrode is disposed in an outlettube that accepts the plating solution after exiting the reactionchamber.
 4. A system as claimed in claim 3 and further comprising acontrol valve disposed to control plating solution flow through theoutlet tube as it flows toward the auxiliary electrode.
 5. A system asclaimed in claim 3, further comprising a particulate filter disposed tofilter residue from the plating solution after exiting the plating bath.6. A system as claimed in claim 1, and further comprising a reservoircontainer, the reaction container disposed at least partially in thereservoir container, plating solution exiting the reaction chamberflowing into the reservoir container.
 7. A system as claimed in claim 6wherein the auxiliary electrode is disposed in the reservoir container.8. A system as claimed in claim 6, wherein the auxiliary electrode isdisposed in an outlet tube that accepts plating solution exiting thereservoir container.
 9. A system as claimed in claim 8 and furthercomprising a control valve disposed to control plating solution flowthrough the outlet tube as it flows toward the auxiliary electrode. 10.A system as claimed in claim 6 wherein the reservoir container isattached to a plating solution outlet tube comprising a particulatefilter.
 11. A system as claimed in claim 1 wherein the second electrodeis a consumable anode and wherein the system further comprises an anodeshield positioned to shield the anode from direct or oblique impingementby flowing plating solution.
 12. The system of claim 11 wherein theanode shield is made of a dielectric material.
 13. A method foroperating a system used to electroplate a semiconductor wafer, thesystem comprising a first electrode for contacting the semiconductorwafer, a second electrode functioning as an anode during electroplatingof the semiconductor wafer, an electrically conductive plating solutiondisposed in a reaction chamber, and an auxiliary electrode disposedexterior to the reaction chamber and a fluid flow path of platingsolution exiting the reaction chamber, the semiconductor wafer and firstand second electrodes being in contact with the plating solution in thereaction chamber during electroplating of the semiconductor wafer, themethod comprising the steps of: providing a flow of plating solutionfrom the reaction chamber to the auxiliary electrode to create anelectrically conductive path between the first electrode and theauxiliary electrode; applying electrical power between the firstelectrode and the auxiliary electrode in which the auxiliary electrodefunctions as a cathode and the first electrode functions as an anode tothereby remove at least a portion of a metal electroplated onto thefirst electrode during a prior semiconductor wafer electroplatingoperation.
 14. The method according to claim 13 and further comprisingthe step of passing the plating solution containing removed plateddeposits through a particulate filter to define a filtered platingsolution.
 15. The method according to claim 14, further comprisingreturning the filtered plating solution to the reaction chamber.